Microsoft Webhooks: Notification endpoint must respond with 200 OK to validation

Question

Hi,
I want to subscribe to calendar events and I am using the following API call

and I am getting the following error

My code in calendar_notification (notificationUrl) has the functionality to send back 200 OK with validationToken.
But while checking my server logs I realised that this API is not even hitting the notificationUrl.
I have confirmed that notificationUrl is live and responds back if I hit the URL directly on the browser.
Also, My app has the following permissions

I can call all the other types of APIs like me/calendar, create events or even GET subscriptions but can not use POST API

Can someone tell me what am I missing and why am I getting this error?

Answer 1

Hello Sanket Khot,

Thanks for reaching out!

The subscription notification endpoint (specified in the notificationUrl property) must be capable of responding to a validation request as described in Notification Endpoint Validation. If validation fails, the request to create the subscription returns a 400 Bad Request error. Ensure that your API accepts "text/plain" as a Content-Type.

Additionally, you can use the Microsoft Graph Postman collection to confirm that your endpoint properly implements the validation request.

Hope this helps.

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